1. Technical Field
Exemplary embodiments of the present invention relate to an optical scanning device and an image forming apparatus incorporating the optical scanning device, and in particular, to an optical scanning device to scan a surface with light beams and an image forming apparatus incorporating such an optical scanning device.
2. Background Art
Many image forming apparatuses employing electrophotography often employ laser technology. In general, this type of image forming apparatus includes an optical scanning device that scans a surface of a photosensitive drum (hereinafter, to be referred to as a “photoreceptor drum”) with laser beams, thereby forming a latent image on the surface of the photosensitive drum.
The optical scanning device includes a light source, an optical system, a deflector, a rotating polygon mirror, and a scanning optical system. The laser beams emitted from the light source enter the rotating polygon mirror via the optical system before the deflector, are deflected by a reflective surface of the rotating polygon mirror, and directed onto the photoreceptor drum via the scanning optical system. Note that the reflective surface of the rotating polygon mirror is also referred to as a “deflection surface”.
There are two methods to have the laser beams enter the rotating polygon mirror, that is, an underfilled type and an overfilled type. The underfilled type is referred to as a “UF type” and the overfilled type an “OF type.”
In the UF type system, a width of the incident light beam is shorter than a length of the deflection surface relative to a main scanning direction. In this case, all the incident light beam is directed onto the photoreceptor drum. By contrast, in the OF type system, a width of the incident light beam is greater than a length of the deflection surface relative to the main scanning direction. In this case, ambient light around the incident light is not directed onto the photoreceptor drum.
Recently, requirements for a more compact and higher-speed image forming apparatus have become acute. Thus, similarly, a more compact and higher-speed optical device has been required.
However, in the conventional optical scanning device, the more compact and higher-speed optical scanning device has been difficult to be produced without degrading image quality.